Independent comparisons. We may earn from shop links. More info

Seramis vs LECA

Updated: October 2026

You have two amazon.co.uk tabs open: one bag looks like red-brown grit, the other like round clay pebbles. Seramis vs LECA is the same clay family with a different pore and a different job. Open-pore grain stores water in the particle. Expanded pebbles, Hydroleca and LECA grit in this set, move air and drain. Pumice is a third mineral, not a tie-break. The ten packs stay on the [Seramis granules comparison](/hub/fertiliser-soil-and-bark-mulch/seramis-granules). Who should buy Hydroleca or the 1 litre grit is on [best Seramis granules](/hub/fertiliser-soil-and-bark-mulch/seramis-granules/sub/seramis-granules-best).

You have two amazon.co.uk tabs open: one bag looks like red-brown grit, the other like round clay pebbles. Seramis vs LECA is the same clay family with a different pore and a different job.

Our top picks

COMPO COMPO pumice granules 6 L

Best overall

COMPO COMPO pumice granules 6 L
9.4/10about £29.78
View offer
Westland Westland Hydroleca 10 L

Rank 2

Westland Westland Hydroleca 10 L
9.2/10about £13.55
View offer
Invigortex Invigortex LECA grit 1 L

Alternative

Invigortex Invigortex LECA grit 1 L
8.4/10about £7.49
View offer
On this page
  1. 1.What changes in the grain
  2. 2.When to pick which
  3. 3.What this comparison actually sells
  4. 4.Mixing inside one water cycle

What changes in the grain

Seramis-type granules are open-pore clay, pore volume above 80 per cent, fired just under 1,000 °C. A UK 15 litre listing outside this comparison printed pH about 5.6. Water sits in the grain. Watertight pot, soil ball left on, red and blue indicator. A calendar drink is how that pot stays wet. Hydroleca and LECA are expanded pebbles. Hydroleca copy talks about about 1,200 °C, a dense skin and a honeycomb core. Jobs are a top, crocking, a mix and a humidity tray. Used as a closed Seramis store, the top dries and the base stays wet. Pumice is volcanic glass. The Royal Horticultural Society calls it an aerator that still holds some water. COMPO is 2–5 mm, neat, up to 25 per cent, or a 2–3 cm top. One hobby weigh-in put Seramis near 72 per cent of dry weight and LECA near 26 per cent. One experiment, not a standard.

When to pick which

Pick Seramis-type clay for a closed mineral store: cachepot, soil ball left on, indicator instead of a weekly mug. That branded bag is not a listing here. Say so before Hydroleca goes in the basket. Pick Hydroleca or LECA grit for drainage, a decorative top, crocking, a humidity tray, or a blend into compost you already own. Westland lists a 2 cm moist greenhouse-bench layer. Invigortex lists a 20–50 per cent blend. Neither gives you the quarter-volume drink. Pick COMPO when you want 2–5 mm pumice and will pay about £5 a litre for mineral, not for volume. Open-pore clay goes wrong by staying wet. Expanded clay goes wrong by hiding a wet base under a dry top. A drained pot with Hydroleca as a crock is a different cycle from a sealed cachepot of Seramis-type grain.
COMPO COMPO pumice granules 6 L

Testsieger

COMPO COMPO pumice granules 6 L
9.4/10about £29.78
View offer

What this comparison actually sells

Hydroleca 10 L is about £13.55, about £1.36 a litre, 4.6 from 569, first 50 reviews from the United Kingdom. Invigortex 1 L is about £7.49, 4.2 from 13, a one-or-two-pot trial. COMPO 6 L is about £29.78, 4.7 from 319, and those reviews are mostly not from the United Kingdom. No branded Seramis indoor-granule listing sits in this comparison. Compost that names Seramis is outside this versus. Pebbles can be rinsed and reused. Compost cannot.

Mixing inside one water cycle

Mix inside one water cycle. Hydroleca is about one part pebbles to three parts compost. Invigortex says 20–50 per cent. COMPO says up to 25 per cent. A hobby blend of 40–50 per cent LECA plus 20–30 per cent Seramis is practice on another site, not a listing here. A mix does not turn Hydroleca into Seramis. A watertight pot and a quarter-volume drink need open-pore grain and an indicator. A drained pot needs the saucer emptied. Steps are on how to use Seramis granules. Buy Hydroleca for topping, crocking or a tray, the 1 L grit only to test, and COMPO only for pumice. For a closed Seramis store, do not substitute pebbles.

Common questions

Which holds more water?
Open-pore Seramis-type clay holds more water in the grain than a dense-skin LECA pebble. One hobby test put that gap at about 72 per cent versus 26 per cent of dry weight. That is a single experiment, not a standard. Pumice sits between an aerator and a mild store, with colour as the cue on the COMPO bag.
Which is better against root rot?
Neither, until you name the pot. Seramis-type clay fails by staying wet in a closed pot you water too often. LECA fails by a dry top over a wet base. A drained pot with Hydroleca as a crock is the pebble answer. A watertight pot with an indicator is the open-pore answer.
Can I run a closed pot with Hydroleca the Seramis way?
You can fill the pot. You should not expect the same store. Hydroleca is sold for topping, crocking, a 1:3 mix and humidity, not as a Seramis closed-pot fill. Doing it anyway is how the base stays wet while the top looks dry.
Is pumice closer to Seramis or to LECA?
Closer to an aerator than to either clay system. COMPO’s 2–5 mm bag is volcanic glass, used neat, at up to 25 per cent, or as a 2–3 cm top. The Royal Horticultural Society treats pumice as a houseplant-media aerator. It is not open-pore fired clay and not a Hydroleca pebble.
Which bag in this set is LECA?
Westland Hydroleca 10 L is the LECA-type volume bag. Invigortex 1 L is washed LECA grit. COMPO is pumice. The other rows are composts. There is no branded Seramis listing in this comparison.
Can I mix them?
Yes, inside one water cycle. Use the ratio on the bag you hold: 1:3 Hydroleca, 20–50 per cent grit, up to 25 per cent pumice. Hobby blends that add Seramis to LECA are practice, not a listing here. A mix does not change a drained pot into a closed Seramis pot.
Which is cheaper per litre here?
Hydroleca at about £1.36 a litre. COMPO pumice at about £5 a litre. Invigortex grit at about £7.50 a litre. Those are rules of thumb from the stored amazon.co.uk prices. The small grit bag is a trial, not a value win.

Related pages

Seramis granules buying guide

Seramis granules

Best clay granules for houseplants UK: which bag fits

Clay granules for houseplants: caps, gnats and trays

How to use Seramis granules: pot, ratio, first water

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings in the stored pages. A gnat, watering or CO2 line is the manufacturer's claim. Peat-free means those words on that listing. This is not a laboratory test.

  1. Seramis, granules and hydroponics (retrieved October 2026)
  2. Seramis, common questions (retrieved October 2026)
  3. Seramis 15 L granules on amazon.co.uk (retrieved October 2026)
  4. Westland Hydroleca clay granules (retrieved October 2026)
  5. Westland orchid potting mix (retrieved October 2026)
  6. RHS, growing media for houseplants (retrieved October 2026)
  7. RHS, peat-free compost (retrieved October 2026)
  8. Written answer on peat sales, 19 March 2026 (retrieved October 2026)